Cleaning, namely detergent, products in liquid form are often of a more convenient use than granular, powder products because they can be formulated in concentrated form and can be easily dissolved in the washing water of fabric or dishwashing machines. In spite of this, liquid detergents have limitations related to the stability of certain ingredients which are commonly used in detergents and softeners.
Liquid detergents are normally either isotropic liquids or structured liquids. They are mostly formed of combinations of anionic surfactants (linear alkylbenzenesulfonate, alkylsulfate, alkylsulfonate), soaps, non-ionic surfactants (alkyl ethoxylate, alkylpolyglucoside, sorbitan esters), builders (citrate, soap, sodium tripolyphosphate, zeolite), antifoam agents (silicone) and optionally combinations of various enzymes. All such consumer product bases contain perfume, typically in the range of at least 0.1 to 1% by weight, of the weight of consumer product. Some bases, in particular isotropic liquids, contain a significant concentration of hydrotrope such as 1,2-propanediol, glycerol, triethanolamine, diethanolamine, monoethanolamine and ethanol.
All liquid detergents contain large concentrations of surfactants (10-60% by weight) and typically water (40-80% of the total formula). They can be found on the market mainly in two formats, the so-called “regular” formulations (typically 10-25% by weight of surfactant content) and “concentrates” (typically 25-50% surfactant content). Typical examples of such formulations can be found for example in the textbook “Formulating detergents and personal care products” by Louis Ho Tan Tai, 2000, pages 156 to 172.
Liquid fabric-softeners typically contain high levels of softening agents with low levels of additives such as calcium chloride, fatty acids, non-ionic surfactants, ethanol, isopropanol, polyethylene glycol. Most commonly used softener actives are twin chains of cationic surfactants such as salts of distearyldimethylammonium, quaternary dialkylimidazolines and, in more recent products, diester quats such as those described in detail in US patent Application 2002/0011584 A, to S.C. Johnson & Sons, for example. Commercial fabric-softeners can be found mainly in two formats, the “regular” formulations (typically 3-10% by weight of softening active content) or “concentrates” (typically 10-20% by weight of softening active content). Typical examples of such formulations are also described in detail in the textbook of Louis Ho Tan Tai above-cited, pages 174 to 185. Most fabric softeners contain a very high level of water, typically from 70 to 95% by weight of the formulation.
The perfume contained in liquid detergents and fabric-softeners is deposited on the fabrics through the wash cycle but is lost over time, upon drying of the washed fabrics and slow evaporation thereafter. In order to prolong the perfume perception by the user of laundered fabrics, it has been taught in the literature to control the release of said perfume by encapsulating it into microcapsules. One class of microcapsules particularly suitable for this aim is that of core-shell capsules made of an inner core of liquid perfume oil enclosed in a thin shell of a polymeric material. Polymeric shells made of the reaction products of an amine, typically selected from urea and melamine, with an aldehyde, typically selected from formaldehyde, acetaldehyde and glutaraldehyde, are very commonly used for this purpose as they withstand the washing cycle of the fabrics and are transferred in a relatively intact form onto the fabrics. Rubbing of the latter during use allows controlled release of the perfume for a longer period of time than would otherwise be the case if the fragrance was not encapsulated. The use of such microcapsules has already been described in EP 0 397 246 B1, to cite but one example, to achieve controlled release of perfume on fabrics washed with various cleaning products such as granular or liquid laundry detergents and fabric-softeners.
However, it has been found that in liquid laundry detergents and fabric softeners containing high levels of surfactants (>5%, cationic or anionic or non-ionic) and water (at least 30% wt), the stability of such capsules is relatively poor. Over time, the encapsulated perfume leaks out of the microcapsule and can be found as free, un-encapsulated perfume in the product. It is believed that this leakage is driven by the high surfactant level in these formulations. Such problems have been quite extensively outlined in the patent literature, of which one can cite by way of example International patent application WO 02/074430, to Quest International, which discusses the above-mentioned stability problems of aminoplast capsules in aqueous surfactant-containing products and suggests a solution based on the use, in the capsule shell, of a second polymer comprising a polymer or copolymer of one or more cyclic anhydrides.
Another example of the manner in which this problem can be obviated can be found in International publication WO 2005/017085, filed by the Applicant, which addresses the same problem and cites prior art examples of the ways in which such fragrance microcapsules can be improved to become more stable in high surfactant and/or softener content liquid products. To this date however, no solution has provided a liquid product of this type having a microcapsule shelf stability beyond 2 months at 45° C., i.e. under storage conditions that are encountered in many practical circumstances.
So, it is an implication from the prior art that the major problem with the use of aminoplast or aminoresin capsules in liquid detergent and fabric softener products is the fact that the perfumed capsules are unstable in such liquid formulations. The perfume gets extracted out/off the capsules by the surface active ingredients in the formulation.
Amongst the various types of liquid consumer products currently used for cleaning and/or treating and softening a great variety of surfaces such as skin, hair, hard surfaces such as tiles, windows, kitchen and bathroom surfaces, or yet fabrics, there exist the so-called anhydrous or non-aqueous formulations. These products, unlike what is the case with aqueous liquids, can also contain bleach.
In such anhydrous or non-aqueous liquid products, an hydrophilic organic solvent is used to replace water. The hydrophilic organic solvent used to replace water can be a water-soluble non-ionic polyoxyethylene-polyoxypropylene copolymer (such as in U.S. Pat. No. 3,169,930 or GB 1455283, to Witco Chemical Corp), a low molecular weight polyethylene glycol (such as in U.S. Pat. No. 4,929,380 to Henkel), a glycol ether, an ethanolamine, or a low molecular weight alcohol or amine.
The amount of water in these products is typically below 10%, by weight, more preferably below 5% by weight, and in any case much lower than in aqueous liquid detergents or fabric softeners which contain typically 50 to 90% by weight of water. Thus, it is understood here that, when talking of anhydrous, near anhydrous or non-aqueous liquid products, we mean by this a liquid product that does not have more than 10% by weight of free water content.
As cited above, unlike aqueous liquid detergents, anhydrous or non-aqueous liquid detergents can also contain bleach (such as suspended perborate, as described in U.S. Pat. No. 4,800,038 or U.S. Pat. No. 5,057,238, to Colgate-Palmolive, or percarbonate), bleach activators (such as TAED, sodium nonaoyloxybenzenesulfonate, N-acyl caprolactam, glyceryl triacetate, or diketones as described for example in U.S. Pat. No. 5,437,686, to Colgate-Palmolive), or a bleach catalyst (such as 1,4,7-triazacyclononane). The bleach system can also be a preformed organic peracid, R1—COOOH, such as described in US 2001/0001786, to G. Scialla.
In anhydrous or non-aqueous fabric softeners, the softener active can typically be a salt of a quaternary ammonium or imidazolinium (such as in U.S. Pat. No. 4,851,141 to Colgate-Palmolive or US 2004/0142840 to Procter & Gamble), an amido-amine (such as in WO 2004011585 to Colgate-Palmolive), clay alone or in combination with an organic softener (as in WO 2004/011586 to Colgate-Palmolive), silicone (as in US 2004/0142841 to Procter & Gamble) or a combination of organic softeners (such as fatty alcohols, fatty acids and esters, long alkyl chain non-ionic surfactants).
Such anhydrous or non-aqueous formulations of liquid detergents or fabric softeners can be sold as liquids in bottles or packaged in water-soluble containers (one of the first examples is cited in US 2003/0148908 to J. Michel et al.). Recently, much attention has been given to the formulation of such water soluble packages or pouches, allowing for single unit dosage in particular, and the interested reader will find significant descriptions thereof in recent documents such as U.S. Pat. No. 6,492,315 and U.S. Pat. Nos. 6,495,503, 504 and 505 to Colgate-Palmolive, US 2004/0142840 and 841 to Procter & Gamble, WO 02/102955 to Unilever, EP 1 400460 B1 and EP 1 462 514 A1 to Unilever, US 2004/0209793 to D. Fregonese, and US 2003/0148908 to J. Michel et al., amongst others, as well as in the prior art specifically cited in these documents as being pertinent in this context.
Such containers are often made of a water-soluble film of polyvinyl alcohol. Several such products have been launched in Europe over the past three years, containing anhydrous or non-aqueous liquid detergents in polyvinyl alcohol sachets.
Despite the large amount of prior art related to the formulation and packaging of anhydrous detergent and softener products, there are very few reports of particular forms of fragrance carriage in these products for the treatment of fabrics, hard surfaces, skin or hair, making it possible to achieve long lasting perfume delivery from the fabrics or other surfaces treated therewith.
This clearly contrasts with the extensive descriptions of the use of fragranced microcapsules for this purpose in aqueous liquids or powder products of the same category, i.e. intended for the treatment of a variety of surfaces. The fact that anhydrous or non-aqueous liquid detergents or softeners typically contain a higher concentration of active ingredient (anionic and non-ionic surfactants in liquid detergent, softener active in fabric-softener) than their aqueous liquid detergents or fabric-softeners counterparts is not strange to this. One would in fact have expected the leakage of perfume from microcapsules incorporated in anhydrous liquid products to be even more extensive than what is the case with aqueous liquids, and therefore expect no perfume release improvement with anhydrous liquid products carrying encapsulated perfumes.
Yet, we have just established, very surprisingly in view of the prior art, that the use of particular aminoplast fragrance microcapsules in anhydrous liquid soaps/detergents and conditioners/softeners is not only efficient but unexpectedly useful and advantageous. Provided that the water content in the formulation is kept below 10%, and preferably below 5%, the surfactant level in this low water/anhydrous formulation can be very high and yet the microcapsules will still be significantly more stable than in similar, high-water formulations.
This is a totally unexpected result in view of the prior art accepted principles that fragranced aminoplast microcapsules are unstable in high surfactant or softener containing liquid consumer products. Furthermore, it makes it possible to effectively deliver perfume onto the surfaces treated with such non-aqueous consumer liquids, in particular bleach containing liquid products.
The prior art is totally silent with regard to this problem of improved fragrance delivery from non-aqueous liquids onto fabrics and other surfaces. Although there have been some reports of construction of stable particles for incorporation in liquid compositions, in particular in anhydrous liquids, they have mostly concerned the physical dispersion stability of the product, i.e. they have been intended to solve the problem of sedimentation or agglomeration of particles containing the actives, which may lead to an inhomogeneous structure of the end product and thus reduced efficacy thereof. In this context, one can cite in particular U.S. Pat. No. 6,673,763 to Novozymes A/S and the prior art documents cited therein, namely on column 1, lines 49 to 60, as well as WO 00/066704 to Procter & Gamble.
To the best of our knowledge, these documents deal with either the encapsulation of detergent ingredients other than the perfume or they do not describe or suggest the use of fragrance aminoplast capsules in anhydrous liquid detergents or softeners.
Moreover, although US 2004/0142840 (hereinafter, the “840” document) and US 2004/0142841 (hereinafter, the “841” document) suggest that perfumes can be used in a form comprising a coating agent or a carrier (see respectively, §[0140] of “840” and §[0154] of “841”), this is clearly a general statement relating to the widely accepted use of encapsulated perfumes in laundry products in general and there is no specific teaching or suggestion that one could expect any particular advantage or improvement by using fragranced aminoplast capsules in particular in non-aqueous laundry treatment liquids. The inventors claim that they obtain more efficient deposition of the perfume with the unit dose fabric products disclosed, but this would appear to be related to the nature of the surfactant and softener system used, which is claimed to have improved cleaning and softening activity (see for example, the “Benefits” section, §[0243] of the “840” document, respectively [0243] of the “841” document).
In this context, one can also cite U.S. Pat. No. 5,480,575, to Lever Brothers, which proposes dissolving detergent reactive adjuncts in biopolymers. Although perfumes are cited as possible such adjuncts, there is no specific description or example of the manner in which perfumes might thus be encapsulated and incorporated in the non-aqueous liquid detergents which are the preferred object of this patent.
Finally, U.S. Pat. No. 6,194,375, to Quest International, discloses fragranced polymer particles suitable for incorporation into compositions comprising surfactants or active softening ingredients. The particles taught may be prepared from aminoplast resin microcapsules, but they carry on their exterior or within the capsule a further hydroxy-functional polymer, preferably highly hydrolysed polyvinyl alcohol. Although there is a general mention in this document (see column 10, line 18) that the taught particles can be used in liquids possibly having “a non-aqueous phase” (not clear what is effectively meant by this), all the examples relate to either solid products or to liquids having a high water content.
Despite the abundant literature existing on the preparation and use of aminoplast resin microcapsules, to the best of our knowledge, there is no prior art disclosure or suggestion of the present invention as herein claimed and advantageously used.